For too long, Democratic leaders have convinced their fellow elected officials that bland, nonconfrontational and incremental centrism is the way to win elections and make progress. In truth, it’s just the easiest way to protect the balance of power in Washington. But by trying to meet a corrupt Republican Party halfway, instead of taking clear stands for what’s right, they have failed to define the party and failed to protect their constituents.

We see the same approach on impeachment: As a way to delay making a decision, Democratic leaders have insisted on waiting for the special counsel, Robert Mueller, to deliver his report. But now the investigation is at risk, because Mr. Whitaker could prevent the special counsel’s team from reaching a just conclusion or even releasing its findings to the public.

The current, Republican-led Congress could have already taken action to shield Mr. Mueller or to put Mr. Trump in check. It still can. If it does not, House Democrats must prepare subpoenas, to be issued as soon as they take over, to ensure that the public learns the truth uncovered by the special counsel, and call on his team to testify under oath in public hearings.